This lesson continues the Internet layer and looks at subnetworks, Classless Inter-Domain Routing (CIDR), subnetting, and supernetworks. Activities include IPv4 subnetting, and using the Cisco Subnet Game.

The first address on any given IPv4 network or subnet is reserved for the network itself.[7]

The last address on any given IPv4 network or subnet is reserved for broadcast.[8]

The separation of the network prefix/subnet number from the host identifier is performed by a bitwise AND operation between the IP address and the (sub)network mask.[9]

The number of subnetworks created by subnetting can be calculated as 2n, where n is the number of bits used for subnetting.[10]

The number of available hosts on each subnet can be calculated as 2n-2, where n is the number of bits available for the host identifier.[11]

The goal of Classless Inter-Domain Routing was to slow the growth of routing tables on routers across the Internet, and to help slow the rapid exhaustion of IPv4 addresses.[12]

Classless Inter-Domain Routing is based on variable-length subnet masking (VLSM), which allows a network to be divided into variously sized subnets, providing the opportunity to size a network more appropriately for local needs.[13]

The benefits of supernetting are conservation of address space and efficiencies gained in routers in terms of memory storage of route information and processing overhead when matching routes.[14]

A binary operation that takes two representations of equal length and performs the logical AND operation on each pair of corresponding bits. The result in each position is 1 if the first bit is 1 and the second bit is 1; otherwise, the result is 0.[15]

CIDR notation

A compact specification of an Internet Protocol address and its associated routing prefix.[16]

provider-independent address space

A block of IP addresses assigned by a regional Internet registry (RIR) directly to an end-user organization.[17]

routing table

A data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes.[18]

A bitmask that encodes the (sub)network prefix length in dotted-decimal notation, starting with a number of 1 bits equal to the prefix length, ending with 0 bits, and encoded in four-part dotted-decimal format.[20]